The electrochemical performance of a La-Mg-Ni-Co-Mn metal hydride electrode alloy in the temperature range of −20 to 30 °C

The effect of temperature on the overall electrochemical properties of La_0.7Mg_0.3Ni_2.875Co_0.525Mn_0.1 hydrogen storage alloy has been studied systematically. The results show that temperature has a striking effect on the overall electrochemical properties, especially the electrochemical kinetic performance. The maximum discharge capacity and the high rate dischargeability (HRD) of La_0.7Mg_0.3Ni_2.875Co_0.525Mn_0.1 alloy electrode both decrease with decreasing test temperature, mainly due to the slower hydrogen transfer in the bulk of the alloy and the lower electrocatalytic activity at lower temperatures. Detailed studies on the temperature effect on the polarization resistance (R_D), the exchange current density (I₀), the limiting current density (I_L) and the hydrogen diffusion coefficient (D), indicate that the diffusion of hydrogen in the bulk for La-Mg-Ni-Co system hydrogen storage alloy electrodes is the rate-determining factor for the discharge process of the alloy electrode for the temperature over 10 °C and the charge-transfer reaction is rate-determining step at lower temperature.     

Growth of 20 mol% Gd-doped ceria thin films by RF reactive sputtering: The O2/Ar flow ratio effect

The search for optimal materials and the utilization of proper manufacturing techniques to replace conventional electrolytes are our research objectives for the operation of solid oxide fuel cells under intermediate temperatures. Furthermore, understanding the effects of process parameters will be helpful for obtaining suitable materials for applications. In this study, we investigate the O₂/Ar flow ratio effect by employing RF reactive sputtering to fabricate 20 mol% Gd-doped ceria (20GDC) films on alumina substrates. The morphology of films was aggregated by nano-scale size of grains which gradually reduced in size from lower to higher O₂/Ar flow ratios. The microstructure of films was transferred from incomplete oxidized materials to well-crystallized cubic fluorite structures using an increased O₂/Ar flow ratio up to 0.30. The oxygen/metal ratio of films was increased gradually and saturated around 2.05 for O₂/Ar flow ratios over 0.25 and remained in uniform composition through whole films for each flow ratios.